Constraining glacial ice and water movement using microseismic earthquakes

Abstract

An array of 13 geophones and CMG-6TD sensors was deployed for two months on Vatnajökull Ice Cap, Iceland, to monitor subglacial seismicity and deeper volcanic seismicity. The main array was deployed on the upstream end of Skeiðarárjökull Glacier to record icequakes from the base of the glacier to investigate the hydrological system using temporal and spatial variation of source mechanisms. For comparison, and to help constrain deeper volcanic seismicity, a smaller sub-array was deployed around the Grimsvötn caldera and a single station was deployed over Bárðarbunga where deeper volcanic activity was known to be present. This seismic array was embedded within a broader array of 3-component seismometers operated by Cambridge University. Data were successfully recorded for up to 52 days although tilt of the 6TD instruments compromises much of their data. Although data are dominated by surface crevassing noise, a number of basal icequakes have been identified which are being used in a cross-correlation event search to identify clusters of events. Once a full event catalogue has been produced, source mechanisms and seismic anisotropy in the ice column will be analysed to constrain ice rheology and dynamics.